A conventional controlling device 100, as illustrated in FIGS. 3(a) and 3(b), has, within a main unit case 101, a circuit board 102 on which is mounted a light source 102a, such as an LED (light emitting diode) that is turned ON in response to a specific operation of the controlling device 100. Moreover, on the front side of the main unit case 101, a front panel 103 is provided wherein a light source displaying window 103a, for displaying the operating status, or the like, of the controlling device 100, is positioned facing the light source 102a. The controlling device 100 that is configured in this way makes it possible for an operator to confirm visually, through the light source displaying window 103a, the current operating state of the controlling device 100, through turning ON/OFF a corresponding light source 102a in accordance with the operating state.
As illustrated in FIG. 3 (b), this conventional controlling device 100 is structured with two stepped frame portions 101a and 101b formed in the inner wall of the main unit case 101, where the circuit board 102 is disposed in the rear stepped frame portion 101a of the main unit case 101, and the front panel 103 is fitted into the front stepped frame portion 101b of the main unit case 101.
If here the color of the controlling device 100 is uniformly black, then the front panel 103 can be given a black color through silk screen printing black ink on the back face of the translucent plastic. However, usually black ink includes carbon, and thus there is a danger that when the user touches the connecting part between the main unit case 101 and the front panel 103 that static electricity will flow through the black ink that is printed on the front panel 103 into the circuit board 102 that is disposed within the main unit case 101.
Given this, as countermeasures for static electricity in the conventional controlling device 100, as illustrated in FIG. 4, a circuit board 102, having a conductive layer 105 formed through printing carbon ink onto the surface thereof, is disposed on the back face side of the front panel 103 that has an operating key 104, and this electrically conductive layer 105 is connected through a supporting plate 106 to a bracket (ground member) 107 that is disposed within the controlling device 100, so that when the user operates the operating key 104 any static electricity charged in the user will flow from the electrically conductive layer 105 to the ground member 107, structured so as to protect, from the static electricity, the electrical circuitry such as the control circuits, and the like, that are provided within the controlling device 100 (See, for example, Japanese Unexamined Patent Application Publication 2005-158579 (“JP '579”)).
However, the controlling device 100 disclosed in JP '579 requires the provision of the ground member 107, and when used in a small controlling device there is a problem in that it is not possible to secure space for the positioning of the ground member 107, and a problem in that the structure is complex if a ground member 107 is used.
Additionally, in the conventional controlling device 100, the structure is one wherein two stepped frame portions 101a and 101b are provided within the main unit case 101, to secure the circuit board 102 and the front panel 103, and thus the size of the circuit board 102 must be small, and there is a problem in terms of constraints on the design due to the limitation of the space for the positioning of the light source displaying windows 103a, which is formed facing the position of the light source 102a that is mounted on the circuit board 102 to being toward the interior of the front panel 103.